Arizona’s largest electric utilities are joining a new power purchase market officials say will give them more price certainty and reliability, estimating the move will save nearly $100 million.

Arizona Public Service Co., Salt River Project, Tucson Electric Power and UniSource Energy Services are joining Southwest Power Pool’s Markets+, which will allow the utilities to purchase power needed for the next day.

“SRP’s participation in SPP Markets+ is a key component of our plan to meet the growing energy needs of our customers reliably and affordably and will help us achieve our 2035 Sustainability Goals,” said Josh Robertson, SRP director of energy market strategy, in a press release.

The move comes with renewable power in mind, as the market will support the addition of more solar and wind energy, officials said in a press release Monday.

Power purchase markets allow utilities to buy power when they need it — during hot summer months for example. Utilities may opt to purchase power rather than starting one of their own power plants based on several factors. They also may look to sell excess power when they are overproducing.

The Arizona utilities will begin participating in the new market as early as 2027, officials said.

“Arizona is one of the fastest growing states in the country and we are thoughtfully planning for the future and evolving our operations to continue to provide top-tier service and reliability to our customers at an affordable cost,” said Brian Cole, APS vice president of resource management.

Markets+ will give Arizona utilities more access to renewable sources to buy power but also to sell power, officials said.

Officials expect to see increased grid reliability as market participants are utilities through out the West and will offer short-term, long-term and day-ahead markets.

For information on Markets+, visit spp.org/marketsplus.